1. Field of the Invention
This invention relates to signal generation for seismic systems, radar systems, sonar systems, secret communication systems, etc. More particularly, the invention is concerned with signal generation with continual change or correction in the signal in response to the signal environment.
2. Brief Description of the Prior Art
In communications systems utilizing correlation techniques in seismic applications, there are many forms and heretofore little or no efforts have been given to the problem of forcing the transmitter to transmit information at the highest possible rate or to automatically design, or self-design on line in the field, an optimized or code or families of codes to evade the particular type of surface noise encountered or to optimize the return from a particular group of reflecting interfaces relative to another group of reflecting interfaces. There has been little or no effort to force to the practical limits the maximum use of the available band width of the earth and the band width of the excitation system, optimally managed or balanced with the optimized use of the band width of the receiving and recording equipment.
There has also been little or no effort made to optimally manage the equipment and the excitation program for the overall maximum return of information while on line in the field. All efforts have usually been made to obtain a redundant amount of data in the obvious prominent center of the band pass of the returning signals. Practically all the redundant efforts and techniques degrade the available band width but improve the signal to noise ratios. A final whitewash pass has been used by means of spiking filters and deconvolution operators to cover up the field problems and to improve the apparent band width. Few efforts have been made to manage the troublesome low end and high end of the seismic spectrum.
The various equipment and the operators, by tradition and habits, work near the center of the available band pass of the equipment and the earth; using CPU's long after the field crew has left the location to clean up and whitewash the narrow band width noisy data with various computer oriented techniques. The problems are quite complex with the result that input efforts have been directed to solution of the gross problem with the gross management of the spectrum leaving much to be desired. The final result has been a narrow band width limited wavelet with unstable characteristics because of random variations of the transmission channel under gross systematic input programs.
The response of the earth to broad band signals is passive and random. Measuring equipment should be capable of adapting with variable efforts and variable strategies. Variable strategies would be in the form of self design on line evasive codes and variable input efforts for each slice of the usable seismic spectrum. This spectrum is generally 4 HZ to 1,000 HZ and is extremely variable.
Signal generators which have been available heretofore for seismic exploration systems, communications systems, radar, etc. have been incapable of production of signals in a systematic form or in a random manner. Prior art signal generators have not been variable and adaptable with fast feedback loop specifically designed on-line for encountered problems to produce a large variety of signals. In particular, prior art signal generators have not been available which would produce random signals and also systematic signals which may be varied on-line as needed in accordance with the environment in which the equipment operates.
In seismic exploration applications, there has been a need for measuring or exploration equipment which is capable of self management to cope with the encountered situations. There has been a need for equipment which could null over or self seek the white wavelet, or correlation function with optimized band width, with minimum side lobes for all travel time paths in variable environment. The white wavelet with maximum band width and minimum side lobes, divorced from the effects of its neighbors, stabilized for the effects of the transmission paths represents the maximum amount of information that can be obtained. Obtaining this white wavelet in a randomly or systematically varying environment is a principal purpose of this invention.